Rheem Water Heater Error Code A105 [Causes and Fixes]

Rheem Water Heater

The Rheem water heater is a good choice for a hot water storage tank. The lower element is at the bottom of the heat pump. It controls the flow of refrigerant into the heat pump. When it malfunctions, the unit will have a higher temperature than normal. The error code will show that the temperature is too high.

Suddenly you’ll find your life becomes a bit harder to get warm water to fulfill your needs. In this article, we are going to find the reason and solution to the Rheem A105 Water Heater Error.

Reasons for Rheem Water Heater Error Code A105

The main reason for the A105 is the heat pump temperature malfunction. When there is a malfunctioning in the heat pump, this is not a normal situation. The reason is the thermostat in the heat pump is malfunctioning.

When this happens, it is not a problem if the heat pump is working properly. The main problem occurs when the heat pump temperature is too high. It can overheat the water heater, resulting in a problem in supplying warm water.

Some of the other reasons for Error Code A105:

  1. Heat pump temperature malfunction
  2. Defective electronic control module
  3. Power drain caused by low system load
  4. Too Much Heat

Heat Pump Temperature Malfunction

The water heater error code A105 is typically caused by a malfunctioning temperature sensor. Faulty wiring could also cause this code. It can also be caused by a bad connection in the Thermistor Circuit Board.

Faulty Sensor

The Thermistor Circuit Board, located in the display, monitors the temperature inside the home. If there is a problem, the water heater will display an error code A105. It is recommended that the thermistors be replaced if get faulty.

If the thermistor control circuit board is in good condition, then a problem with the wiring should be investigated. When the thermistor control circuit board gets damaged, then it’s time to replace it. The thermistor is located at the bottom of the control board. It should be replaced as soon as possible.

Check List:

  • Faulty wiring
  • Faulty sensors
  • Check thermistors connection
  • Check the temperature sensor in the display
  • Replace faulty parts

Defective electronic control module

To be safe, turn off the water supply valve. If the water is hot, open and closes the valve several times to ensure that the water is not turned off inadvertently. Remove the top of the water heater. Check the electronic control module for signs of corrosion or malfunction. If the water heater is new, check the wiring harness.

If you find a loose wire, re-route it, then tighten it. If you can’t locate a loose wire, replace the electronic control module. If the wiring harness is dirty, clean it with an alcohol-based cleaner. If the water heater has a silver coating, replace the electronic control module. If you have a stainless-steel water heater, replace the electronic control module.

Power drain caused by low system load

The control module is the main component of your water heater. It is responsible for measuring the power load in your machine and determining how to operate it. The control module also relays the information to the water heater, which then indicates the water temperature. If the power load is too low, the control module is unable to accurately determine the operation. A105 is due to a sensor problem, your home should be checked for low power loads. This could cause the control module to issue an error code.

Too Much Heat

The thermostat is probably stuck. When the thermostat is stuck, it will not let water flow through, causing the pressure relief valve to open and the water heater to shut off. The problem is most likely the fault. Your water heater could be in need of a service. First, replace the thermostat.

If that doesn’t fix the problem, replace your pressure relief valve. If the heating elements are worn out, you can replace them. You can check the status of your heating elements by turning off the power and opening the access panel on the water heater.

You should then be able to remove the two heating elements and inspect them for any signs of wear. If that doesn’t fix the problem, replace the whole water heater.

How to Solve the Error Code A105 of Rheem Electric Water Heater?

To solve the error follow the process:

  1. Test the Thermistors
  2. Check the Sensor Reading
  3. Confirm the Reading on the Ohm Reading

Test the Thermistors

The thermistors are located at the bottom of the tank and are part of a thermostat that regulates the temperature of the water. If any of the thermistors are open, the circuit will not work and the error code A105 will appear. Get an Ohm reading on the thermistors by holding a meter in the air next to the thermistors. The Ohm chart on the packaging should be used to determine the correct reading.

If you do not have an Ohm meter, you can use a piece of wire or a piece of paper to approximate the readings. The wrong temperature for a particular thermistor will cause the thermistor to get too hot or too cold. The thermistors will need to be replaced if the readings are not accurate. The error code A105 will be cleared if you replace the thermistors.

The water temperature should be checked after the thermistors are replaced. The water heater should be working properly again.

Check the Sensor Reading

Read the sensor value on the water heater display by selecting Service>Sensors. If the sensor is showing +250°F the car kit must have a problem somewhere. If the sensor shows – 40°F, the circuit is open.

The shorted circuit cant operate the water heater properly. You’ll have to replace the sensor. The sensor could be bad or the wiring harness could be broken.

Sensor Wiring

Confirm the Ohm Reading

The error code A105 is caused by the sensor or the wiring harness is bad or it could be the circuit board. Now it’s time to confirm the reading on the Ohm chart.

Turn the water heater OFF, disconnect all the wires from the sensor, open the tank lid, and touch the meter to the top of the sensor. The chart on the package should be used to confirm the correct reading.

Confirm the reading again on the ohm meter. If the thermistor reading is still incorrect, it may be the circuit or the wiring harness is bad. Replace the thermistor or replace the entire wiring harness if the reading is good.

When doing your research and replacing the sensors and thermistors, try to avoid removing the wiring harness that’s mounted on the heater’s back panel. These are difficult to reinstall and replace correctly.

How Do You Clear a Rheem Error Code?

There are a lot of different problems with your Rheem water heater that can cause a malfunction. The problems are mostly related to problems with the unit itself and will need to be replaced by a certified technician. However, most of the problems can be fixed in a small home repair or an appliance repair. Therefore, you need to find the right technician who can fix the problem quickly.

The Rheem water heater codes are annoying but you can clear them easily. Press the power button for a moment, the code should be gone. This is a code for a defective unit that needs to be replaced. In this case, it is also needed to be replaced to prevent any water damage. But as long as you take care of the unit, it can last a long time.

How to Get a Rheem Water Heater Maintenance Manual?

Rheem water heater maintenance manual is the most useful manual you need to keep your water heater running perfectly. You need to make sure that you have the manual at all times since this manual contains your warranty information, and other important tips to keep your water heater running without problem.

Download the manual from the Rheem support site and keep it with your Rheem unit.

To know how to replace a filter or to know what type of filter you need, download your manual first. You will find a lot of useful tips and information there that you will want to know. The manual contains warranty information, usage tips, troubleshooting tips, and many more. You should refer to it before and after doing any maintenance.

How to Test Thermostat’s Settings?

It is very important to know that your Rheem electric water heater thermostat is set at the right temperature. You will be able to do that if you keep your manual handy and will refer to that manual. The manual includes a graph showing the correct temperature readings.

When doing the thermostat test, do not forget to set the thermostat at the correct temperature. Make sure that you set the thermostat at the correct temperature first. Then you can make sure that the water temperature and heating elements of the water heater are also correct.

If you are unable to set the thermostat correctly, you will also see a red light (not working). Your manual is very important to know how to test the thermostat and is very helpful in preventing problems from appearing. You should be using it at all times.

A very similar error code appears when the thermostat is set too low. You will not see water heating until it is too hot. The code could also appear when the thermostat is set too high.

Your heater will not heat the water at all, and you will not be able to see water when it is too hot. Your manual will also help you know how to test the thermostat so you can prevent this. If the compressor gets faulty, then you might get an A004 error code.

To Recap

The A105 code shows when the Rheem water heater has a temperature malfunction of the heat pump. Faulty wiring can cause the thermostat to fail, overheating the system and showing the error. A faulty thermostat will also fail to detect the operating temperature of the system properly and leads to A105.

Measure the electricity flow of the thermistors, and check the sensor reading by Service>Sensors. Take an Ohm chart to convert the Ohm reading to a temperature reading and match it with the sensor reading.

Generally, the heat pump heats the water. The problem with the heat pump will make the system fail. So, if you encounter this problem, it’s time to replace the sensor. If you can’t fix it by yourself, contact the technician or the support.

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